Okay, I'll bite. Same guy made all 5 of those pipes? Cuz I see a Charatan copy, a blocky Danish freehand, a Zulu that has a lovely piece of briar and pretty loosey-goosey shaping, a billiard that is almost shaped correctly and has a two dollar stem, and a blocky bandsaw-ish take on a zulu.
If a guy is making stems, that usually adds quite a bit of value to a pipe. If he's making stems WELL that adds a lot of value to a pipe. If a guy is executing shapes
well, that adds quite a bit of value to a pipe.
The idea that some or other pipe is a good deal at some or other price point is a little nebulous, but there are certain markers we talk about in pipe making circles, particularly as regards price points and perceived value. Drilling a block of briar correctly and putting a stem in it is pretty easy. Making pipes that hit certain markers in terms of technical execution is another thing entirely, and that's a big separator in the market (which is to say the price, honestly) that the pipes belong in.
Here's two similar pipes I did a few years apart: First one's out of balance, shows a design idea but lacks really "nice" execution.
Do it again, make it better, more balanced, more fluid:
Evolution, as you said.